The pneumatic lighter is an instrument for use in demonstrations which is composed of a cylinder the ends of which are metal; the walls are of the same metal or very thick glass. One of the ends is closed while the other is open to allow insertion of an iron rod with an airtight piston. The rapid and violent raising and lowering of the piston causes an adiabatic compression of the air; the consequent rise in temperature is so sharp that it causes kindling wood previously placed in the cylinder to catch fire immediately. Indeed, a sufficiently quick compression, which reduces the volume by one twelfth of its initial value, causes a rise in temperature of about 500° Celsius.The specimen on display here is made up of a glass cylinder (diameter 2.5 cm, height 21 cm), the walls of which are about 3 mm thick, and the piston is a brass cylinder 3.2 cm long, with a liner of leather to make it airtight. The piston shaft is made of iron and the handle is a wooden cylinder fixed horizontally at the top of the shaft. The extremities are made of brass.